1. Field of the Invention
The present invention relates to an exposure system and method, and particularly to an exposure system and method with recipe compensation for an adjusted exposure device in semiconductor manufacturing.
2. Description of the Related Art
Photolithography is one of the most important technologies in semiconductor manufacturing. It seriously affects structures of MOS devices, such as patterns of layers and doped regions. Typically, the number of masks used in photolithography indicates the complexity of a manufacturing process. As described above, since photolithography is complicated, the exposure device performing the photolithography can create a bottleneck in semiconductor manufacturing.
Exposure of wafers is generally implemented in a “Step and Repeat” fashion to transfer high resolution patterns to the wafers, the exposure device is thus referred to as Stepper. That is to say, the pattern on the mask is projected and sized to one portion or block of the wafer. This is repeatedly implemented for all blocks on the wafer one by one until the entire wafer is exposed.
Since only the pattern of one layer is transferred to the wafer after each block is exposed and there are many patterns of layers and corresponding masks involved in one manufacturing process, piece alignment between the blocks of the wafer, overlay alignment between the patterns of the layers is essential to the photolithography processing step.
However, performance of an exposure device always slightly varies with time. For a precisely accurate exposure, the wafers processed must be measured to compensate for parameters (recipe) used by the exposure device. The recipe will be compensated and used by the exposure device to process the subsequent wafers. In general, the recipe compensation is implemented manually or using a feedback system. Taiwanese Patent 516099 discloses a method and apparatus of wafer exposure with correction feedback that employs a feedback system using a computer system to calculate values and use the values to compensate overlay parameters.
However, 516099 is designed for parameter adjustment between lot wafers processed by the exposure device with time. If the exposure device encounters malfunction or failure, or for routine maintenance purpose, in which the exposure device needs to be adjusted, there is no effective mechanism of recipe compensation for the exposure device. Pilot wafers are processed by the exposure device and then measured to obtain the compensation with some approximate calculations. It is time-consuming and increase the rework rate, thereby resulting in mistakes, and impacting throughput of the manufacturing process.